Cap for hermetically sealed semiconductor



Aug. 9, 1966 G. HILLMAN ETAL 3,255,802

CAPNFOR HERMETICALLY SEALED SEMICONDUCTOR Filed Nov. 18, 196s, I

A/f/g 2 2' INVENTORS 3 Gory H/'l/man if* 5 BY A//an Dov/'s ATTORNEY United States Patent Office L 3,265,802 Patented August 9, 1966 3,265,802 CAP FOR HERMETICALLY SEALED SEMICONDUCTOR f Gary Hillman, Livingston, and Allan Davis, Hazlet, NJ., assignors to Mitronics luc., Murray Hill, NJ. Filed Nov. 18, 1963, Ser. No. 324,516 `8 Claims. .(Cl. 174-15) teristics from the semiconductor, the heat generated by the 20 semiconductor must be effectively dissipated. has become known to mount semiconductors upon `a relatively heavy Imetal body or base forming part of the metal envelope, the mounting base acting as a heat sink. T he* metal envelope in lwhich the semiconductor VVmay be located is customarily made in two parts, viz, ,a flanged cup and atmatching flanged capor `header,the tlanges of these two elements being suitably secured to .each other` (as by coldv Welding or other suitable methods known in the art) thereby to isolate the semiconductor'from the atmosphere; one or more leads in these prior art devices were introduced into the metal envelope, suitable electrical insulating means therefor being provided, :in such a manner and in such relation to the heat sink as to result in a high-profile (i.e., bulky) package.

The present invention is an improvement,over the various means heretofore devised for hermetically sealing and cooling semiconductors.

Very briefly, the present invention is directed tothe cap having a low profile, while effectively dissipating heat generated by the semiconductor.

(3) Y'Manufacturing and assembly costs for the cap or header of the present invention are considerably reduced yover those obtaining for prior art devices.

,One of the objects of the present invention is to provide acap or header for a hermetically sealed semiconductor.

Anotherobject of this invention is to provide a cap or headerfor a"hermetically sealed semiconductor whereby the heat ,generated by the semiconductor is effectively dissipated.

A further object of this invention is to provide a cap or header fora semiconductor device wherein maximum heat transferl surface for etlicient removal of heat from the semiconductor device is attained, wherein the leads may be introduced vinto the metal envelope through that face of ,the insulating ceramic member to which-is secured the heat dissipater'andyet be effectively isolated from each other -while permitting ythe heat dissipating member to be infull facial contact with a heat sink 4or radiator, and wherein the cap or header has a low profile.

Other andfurther objects of this invention will become apparent during the course of the following description.

Referring'now to the drawing, in which like numerals represent likev parts in the several views:

FIGURE l represents a front elevation of the cap or header, showing the plate secured to a face of the ceramic member, the slots in the plate, land the several leads being introduced -into the metal envelope through the ceramic member.

FIGURE 2 represents a vertical section taken along the line `2-.2 of FIGURE l, showing the relative thicknesses of the plate and leads as well as the flange secured to the f, other face of the ceramic member for attachment to the o mating flangeofthe conventional cup forming the other or header of the above-mentionedmetal envelope, 'which 40 cap or header comprises a heataconductive `plate vsecured as by brazing, soldering, or otherwise to one `faceof an electrically insulating ceramic member `in thermalcontact with the semiconductor, which `plate removes wheat generated by the semiconductor and shunted to the ceramic member, and which plate further conducts the Aheat so removed to a heat sink or radiator, the said plate covering substantially the entire face of the ceramic member except for slots which are :formed in the plate extending inwardly from the periphery thereof, which slots provide recesses for leads whichextend through the ceramic member and are connectedto the semiconductor on the other side of the .ceramic member, the thickness of the` plate being slightly greater than the thicknessof the leads, fwhereby a low-profile cap or header is provided which-is effective in disspatingheat generated by the semiconductor.

Several Vadvantages not realized by prior art ,devices are attained by the present invention, viz:

(l) Maximum heat transfer surface betweenthe face of the ceramic member and the plate is provided, and an equivalent heat transfer surface betweenthe plate and the heat sink or radiator (which may be in full facial contact with the plate)islalso provided, making for r`anfefcient dissipation o'f heatgenerated by the semiconductor.

(2) Each of the leads secured to the hermetically sealed semiconductor `is introduced into the metal .envelope throughthe same face of the ceramic member asthe other leads, which face is the same face to which thexplate is secured, all ofthe leads beingY effectively isolated from Y each other, from the plate, and from'the heat sink,where by rthere is provided a cap or header for the metalrenvelope half of the `metal envelope (the said cup and the semiconductor hermetically sealed therein not being necessary yto a full understanding vof this invention and hence not being shown herein).

FIGURE 3 represents a side elevation of this invention, and is generally similar to FIGURE 2 (the conventional flanged cup and the enclosed Asemiconductor not being shown herein).

FIGURE 4 represents a rear elevation of the capaor header.

FIGURE l5 represents an enlarged view of a portion of the cap or header, showing the thickness relation between the plate and one of the leads.

semiconductor; such a conventional flanged cup is shown as element 8 in U.S. Patent 2,939,204, element 1 thereof being the cap or header which completes the metal envelope. v

Secured to the front face of ceramic -member 1 is av rp1ate6 which is substantially coextensive with the front face 3 except for a number of slots 7 which extend inwardly from the periphery of said plate 6 suciently to vprovide a recess for a lead 2, there being one o said slots V7 -for each of said leads 2. Thus, except for-the slots 7 `which are required to isolate each lead 2. from the other leads 2 as shown in the several figures, maximum heat transfer surface between ceramic member 1 and plate v6 is provided. Plate 6 may be formed of a sfxitable heatconductivo material; in the particular commercial application herein disclosed, plate 6 is formed of oxygen-free high-conductivity copper.

Plate 6 is slightly thicker than any of leads 2. As seen in the several figures, leads 2 are brought from outside the metal envelope to front face 3 of ceramic member 1 in a direction parallel to said front face 3 and, specifically, plate 6 and leads 2 are in contact with front face 3 of the said ceramic member 1. Front face 3 being planar, this has the effect of recessing` or` isolating each lead 2 from thevfront face 8 of plate`6 andifrom the other leads 2. Thus, the front rface 8 of plate 6 can lbe placed in full facial contact with a conventional heat sink or radiator (not shown), providing maximum heat transfersurface between said plate 6 and said heat sink or radiator without shorting out leads v2, said heat transfer surface between plate 6 andthe heat sink or radiator being the same as the heat transfer surface between the ceramic member 1 and the plate 6 for optimum results. In this commercial application, a difference in thickness between plate 6 and leads 2 ranging between only 0.008-0.0l2 inch has been found sufiicient and effective in permitting front face 8 of plate 6 to be placed in full facial contact with a heat sink or radiator while electrically isolating' each `of the leads 2. The total thickness of plate 6 ranges between 0.024-0.026 inch, and the thickness of ceramic member 1 ranges between 0.0l8-0.022 inch, in the commercial application shown herein, making for a cap orvheader having avery low `profile or thickness, which low-profile cap still permits maximum heat transfer surface and effective dissipation of heat' from the semiconductor to the heat sink while preventing short circuits between the leads 2. In other commercial applications, other dimensions may be employed, provided leads 2 are behind the plane of front face 8 of plate 6.

Plate 6 maybe secured in any known manner to front face 3 ofvceramic member 1, provided the two are in heatconductive relation. In the commercial application herein disclosed, both faces 3 and 4 of ceramic member 1 are metallized by known methods to the extent desired,` such metallized areas being indicated bythe numeral 9; plate 6, as welll as leads 2 and ange 5, are brazed to their respective metallized areas by known methods, 'such brazed joints providing excellent heat-conductive characteristics as well as a tight seal between the said 'elements and ceramic member 1. The metalliz/ed area or surface associated with plate 6 is indicated by the numeral 9a and is at least coextensive with said plate 6 for optimum heat transfer efficiency. The metallized area 9b shown on rear face 4 of ceramic member 1 (FIGURE 4) provides a suitable surface fo'r attachment of thevsemiconductor thereto byl known methods, facilitating electrical connection between the said semiconductor (not shown) and one of the leads 2 as well as permitting heat generated by the said semiconductor to be shunted to the ceramic member 1, andl in FIGURES 1 and 4, but is equally applicable to other shapes as, for instance, square, rectangular, trapezoidal, oval, etc.; where such alternate l shapes are employed, it

is to be understood that plate 6 may be substantially coextensive with the contact-ing face of the alternate'shape of ceramic member 1 except for slots 7. Moreoveryit is to be understood that this invention is not limited to the specific composition of ceramic member 1 mentioned` herein, but -s equally applicable to other compositions of electrical insulating members. Also, this invention is not limitedv to apparatus including three leads Zas shown herein in one particular commercial application where the f semiconductor is aI transistor, but is equally applicable to placed in heat conducting relation to said serni` conductor,

(c) a heat conductin-g second element adjacent and substantially coextensive with the-second face of said first element and in heat conducting relation therewith,

(d) at least one lead extending from la point outside said envelope to a point within the perimeter of the second face of said first element, said lead being substantially parallel to the second face of said first element, said lead further extending through said first element from the second face thereof tothe first face thereof and adapted to be secured in electrical contact with a portion of said semiconductor,

(e) at least one slot in said second element extending inwardly from the perimeter thereof, said slot providing a recess for one lead,

(f) the depth of said slot being greater than the thickness of said lead. v

2. A header for an envelope adapted to enclose a semiconductor, said header comprising:

(a) an electrically insulating heat conducting first element having a first face and a second face opposite said first face, y

(b) said first fa'ce of said first element adaptbd to be placed in heat conducting relation to said femiconductor,

(c) a heateonducting second element secured to and substantially coextensive with the second face of said first element and in heat conducting relation therewith,

(d) at least one lead extending from ay point outside said envelope to a point within the perimeter of the second face of said first element adjacent the second face of said first element in a plane substantially parallel to the plane of the second face of said first element, said lead further extending through said first element from the second face thereof to the first face thereof and adapted to be secured in electrical contact with a portion of said semiconductor,

(e) at least one slot in said second element extending inwardly from the perimeter thereof, said slot providing a recess for one lead,

(f) the depth of said slot being greater than the thickness of said lead.

3. A header for an envelope adapted to enclose a sem-- conductor, said header comprising:

' (a) an electrically insulating heat conducting first plate havinga first face and a second face opposite sa-id first face,

(b) said first face of said first plate adapted to be placed in heat conducting relation to said semiconductor,

(c) a heat conducting second plate having a first face and a second face opposite said first face, the second face of said second plate being secured to and substantially coextensive with the second face of said first plate in heat conducting relation` therewith,

(d) at least one lead extending from a point outside saidenvelope to a point within the perimeter of the second face of said first plate 4adjacent the second face ofsaid first plate ina plane substantially paralilel to the plane of the second face of said first plate, said lead further extending through said first plate (f) the depth of saidslot being greater than vthe thickness of said lead.

4. Apparatus as in claim 3, further comprising:

(g) liange -rneans secured to the first face of said first plate and adapted to be secured to the remainder of the envelope.

5. A header for an envelope adapted to enclose a semiconductor and further adapted to contact a heat sink or radiator, said header comprising:

(a) an electrically insulating heat conducting first element having a first face and a Isecond face opposite said first face,

(b) said first face of said first element adapted to be placed in heat conducting relation to said semiconductor,

(c) a heat conductingsecond element having a first face and asecond face opposite said first face, the second face of said second element being secured to and substantially coextensive ywith-the second face of said first element in heat'conducting realtion therewith,

(d) the first face of said second element being adapted to facially engage said heat sink or radiator in heat conducting relation therewith,

(e) at least one lead extending from a point outside said envelope to afpoint within the perimeter of the second face sof said first element adjacent the second face of said first element in a plane substantially parallel to the plane of the sec-ond face of said first element, said lead further extending through said first element from the second face thereof tothe first face thereof and adapted to be secured in electrical contact with a portion of said semiconductor,

(f) at least ione slot in said second element extending -inwardly from the perimeter thereof, said slot providing a recess for one lead,

(g) the depth of said slot being greater than the thickness of said lead.

6. A header for an envelope adapted to enclose a semiconductor .and further adapted to contact a `heat sink or radiator, said header comprising:

(a) an electrically insulating heat conducting first plate having flat first and second faces opposite each other,

(b) said first face of first plate adapted to be placed -in theat conducting relation to said semiconductor, (c) a heat conducting second plate having fiat first and second faces opposite each other, the second face of said second plate being secured to and substantially coextensive with the second face of said first plate 4in heat conducting relation therewith,

(d) the first face of said second plate being adapted to be maintained in facial contact with said lheat sink or radiator in heat conducting relation therewith,

(e) at least one lead extending from a point outside said envelope to a point within the perimeter of the second face of said first plate adjacent the second face of-said first plate in a plane substantially parallel to the plane of the second face of said first plate, said lead further extending through said first plate from the second face thereof to the first face thereof and adapted to be secured in electrical contact with a porti-on of said semiconductor,

(f) at least one slot in said second plate extending inwardly from the perimeter thereof, said slot providing a recess for one lead,

(g) the depth of said slot being greater than the thickness of said lead.l

7. Apparatus as in claim 6, further comprising:

(h) 'ange means secured'to the first face of said first plate and adapted to be secured to the remainder of the envelope.

8. Apparatus as in claim 6, further comprising:

(h) said first plate being a ceramic material,

(i) ysaid second plate being `a metallic material.

References Cited by the Examiner UNITED STATES PATENTS 2,887,628 5/1959 Zierdt 317-234 3,187,083 6/1965 Grimes. 3,195,026 7/1965 Wegner et al 174-52 X 3,209,065 9/ 1965 Steiner 174-52 LEWIS H. MYERS, Primary Examiner. ROBERT K. SCHAEFER, Examiner. I. R. RUGGIERO, Assistant Examiner. 

2. A HEADER FOR AN ENVELOPE ADAPTED TO ENCLOSE A SEMICONDUCTOR, SAID HEADER COMPRISING: (A) AN ELECTRICALLY INSULATING HEAT CONDUCTING FIRST ELEMENT HAVING A FIRST FACE AND A SECOND FACE OPPOSITE SAID FIRST FACE, (B) SAID FIRST FACE OF SAID FIRST ELEMENT ADAPTED TO BE PLACED IN HEAT CONDUCTING RELATION TO SAID SEMICONDUCTOR, (C) A HEAT CONDUCTING SECOND ELEMENT ADJACENT AND SUBSTANTIALLY COEXTENSIVE WITH THE SECOND FACE OF SAID FIRST ELEMENT AND IN HEAT CONDUCTING RELATION THEREWITH, (D) AT LEAST ONE LEAD EXTENDING FROM A POINT OUTSIDE SAID ENVELOPE TO A POINT WITHIN THE PERIMETER OF THE SECOND FACE OF SAID FIRST ELEMENT, SAID LEAD BEING SUBSTANTIALLY PARALLEL TO THE SECOND FACE OF SAID FIRST ELEMENT, SAID LEAD FURTHER EXTENDING THROUGH SAID FIRST ELEMENT FROM THE SECOND FACE THEREOF TO THE FIRST FACE THEREOF AND ADAPTED TO BE SECURED IN ELECTRICAL CONTACT WITH A PORTION OF SAID SEMICONDUCTOR, (E) AT LEAST ONE SLOT IN SAID SECOND ELEMENT EXTENDING INWARDLY FROM THE PERIMETER THEREOF, SAID SLOT PROVIDING A RECESS FOR ONE LEAD, (F) THE DEPTH OF SAID SLOT BEING GREATER THAN THE THICKNESS OF SAID LEAD. 